1. Field of the Invention
The present invention relates to a drive apparatus for a zoom lens barrel.
2. Description of the Related Art
A zoom lens includes at least two movable zoom lens groups which are moved in predetermined directions upon zooming. In a first type of conventional or classical drive mechanism which has been used particularly for a single lens reflex camera in which no focal shift during zooming is accepted, the movable zoom lens groups are moved along tracks defined by cam grooves formed on a cam ring so as not to cause a focal shift. In a second type of known drive mechanism for compact cameras or digital cameras in which it is necessary to correctly focus on an object at the time of shutter releasing, the movable zoom lens groups are moved upon zooming while permitting a focal shift, and thereafter the movable lens groups are moved to an in-focus position in accordance with set focal length data and set object distance data upon shutter releasing.
In the second type drive mechanism, separate drive mechanisms for the two movable lens groups are provided, and hence the positions of the lens groups must be controlled. To this end, various types of drive mechanisms have been proposed or used. In conventional drive mechanisms, however, the drive units are harmoniously incorporated in the guide mechanism of the movable zooming lens groups, thus resulting in a complicated assembling operation.